Uplink channel compensation for touchscreen devices

ABSTRACT

An apparatus and method for compensating the effect of a contact by a hand or other body part of a user with a touch screen while holding an input device on the strength of a capacitively coupled uplink signal provided to the input device by a host device, by detecting and/or discriminating the body touch and modifying at least one uplink channel parameter.

BACKGROUND

Electronic devices, especially tablets or smart phones, may accept inputvia hand-held peripheral input devices, such as a pen or stylus, and maythen act as host devices to the input devices. The input device may beheld manually by a user in relation to a touch screen to provide inputto the electronic device. Positions of the input device over the touchscreen are correlated with virtual information portrayed on the touchscreen. A touch position of the input device can be detected due to asmall change in capacitance at a contact point on the touch screen.

SUMMARY

This Summary is provided to introduce a selection of concepts insimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Nor is theclaimed subject matter limited to implementations that solve any or allof the disadvantages noted herein.

According to an aspect, the disclosure in some embodiments relates to anapparatus for controlling an inking process by an input device on atouch screen, the apparatus comprising:

a body touch detector for detecting a body touch by a body portion of auser on the touch screen during a concurrent touch by the input device;and

a modulator for temporarily changing at least one transmission parameterof an uplink channel from a touch screen driver of the touch screen to areceiver of the input device in response to a detected body touch.

According to another aspect, a host device or digitizer comprises theabove apparatus of the first aspect.

According to a further aspect, the disclosure in some embodimentsrelates an apparatus for controlling an inking process by an inputdevice on a touch screen, the apparatus comprising:

a communication unit for receiving a body touch feedback signal from ahost device of the touch screen; and

a sensitivity controller for controlling the sensitivity of a receiverfor receiving an uplink signal from a touch screen driver of the touchscreen, in response to a receipt of the body touch feedback signal.

According to still further aspect, an input device comprises the aboveapparatus of the further aspect.

According to a still further aspect, a method of controlling an inkingprocess by an input device on a touch screen comprises:

detecting a body touch by a body portion of a user on the touch screenduring a concurrent touch by the input device; and

temporarily changing at least one transmission parameter of an uplinkchannel from a touch screen driver of the touch screen to a receiver ofthe input device in response to a detected body touch.

According to a still further aspect, a method of controlling an inkingprocess by an input device on a touch screen comprises:

receiving a body touch feedback signal from a host device of the touchscreen; and

controlling a sensitivity of a receiver for receiving an uplink signalfrom a touch screen driver of the touch screen, in response to a receiptof the body touch feedback signal.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art. Although methods and materials similar or equivalentto those described herein can be used in practice or testing ofembodiments of the disclosure, example methods and/or materials aredescribed below. In addition, the materials, methods, and examples areillustrative only and are not intended to be necessarily limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

To assist understanding of the present disclosure and to show howembodiments of such may be put into effect, reference is made, by way ofexample only, to the accompanying drawings in which:

FIG. 1 is a schematic block diagram of an example system comprising astylus and a host device,

FIG. 2 is schematic block diagram indicating capacitances that influencethe strength of an uplink signal during a body touch on a touch screen,

FIG. 3 is a schematic flow diagram of an uplink channel compensationprocedure during a body touch,

FIG. 4 is a schematic block diagram of an example system with uplinkchannel compensation at a host device, and

FIG. 5 is a schematic block diagram of an example host device withuplink channel compensation at an active stylus.

DETAILED DESCRIPTION OF EMBODIMENTS

The present disclosure is directed to an adaptive uplink channelcompensation for a touch-sensitive display system.

FIG. 1 is a schematic illustration of an example system comprising ahost device 20 (e.g. an electronic device with a touch-sensitive displaydevice, including a smart phone, a tablet, a watch, a desktop computer,a gaming device, a wearable device, a television, a video conferencingsystem, etc.) and a hand-held stylus peripheral (“stylus”) 10 with aninput/output unit 12 for receiving an uplink signal received from thehost device 20. Furthermore, the stylus 10 may comprise a pressuresensor (not shown) configured to sense a pressure or force applied to atip electrode 14 of the stylus 10. The stylus may be capable oftransmitting output data (e.g. measured pressure or force data) of thepressure sensor to the host device 20 via a downlink signal. The hostdevice 20 comprises a touch screen (TS) 22 (touch-sensitive display) andan operating system (OS) 30 for controlling the touch screen 22.

The stylus 10 is used to communicate user input to the host device 20.The touch screen 22 may include a built-in digitizer to sense signalstransmitted from the stylus 10. A user interacts with the digitizer bypositioning and moving the tip electrode 14 of the stylus 10 over asensing surface of the touch screen 22. The position of the tipelectrode 14 of the stylus 10 with respect to the sensing surface istracked by the digitizer and interpreted as a user command. In sometechnologies, the position of the stylus 10 can be determined based ondetection of capacitive coupling between the tip electrode 14 of thestylus and one or more electrodes of the digitizer. For example, thetouch screen 22 may include a digitizer with a plurality of X and Yoriented conductors or a resistive film to receive downlink signalstransmitted from the tip electrode 14 of the stylus 10. To accuratelyidentify the tip position, the transmitting electrode is, in sometechnologies, physically positioned within the writing tip electrode 14of the stylus 10.

The stylus 10 can be classified as a passive stylus or an active stylus.A passive stylus utilizes sensing methods based on changes in thecapacitive coupling between sensor electrodes deposited on atouch-screen sensor and an input object, such as a rubber-tipped stylus.In contrast, an active stylus drives unique modulated downlink signalsbetween the tip electrode 14 of the stylus 10 and a grid or matrix ofelectrodes of a touch-screen sensor of the digitizer and utilizessensing methods based on changes in the capacitive coupling betweensensor electrodes. The digitizer detects at least one position of thestylus 10 based on the downlink signal emitted and the detected positionprovides input to the host device 20 associated with the digitizer. Thedetected position may then be interpreted as user commands. Often, thedigitizer may be integrated with touch screen 22, e.g., to form atouch-sensitive display device.

Furthermore, the stylus 10 may communicate detected pressure informationto the host device 20 for digital ink weighting. One of the features ofdigital ink is force/pressure sensitivity which allows line thicknesscontrol by the user of the stylus 10.

If the stylus 10 is an active stylus it may generate a modulateddownlink signal that may be detectable by the digitizer. The signal maybe encoded with information such as the device identification,operational mode (e.g., writing, erasing), pressure/force information,tilt information, and other information. The information may beallocated to various portions of the signal.

If the stylus 10 is a passive stylus, it may utilize sensing methodsbased on changes in the capacitive coupling between sensor electrodesdeposited on a touch-screen sensor and an input object, such as arubber-tipped stylus. In such implementations, the stylus 10 maycommunicate detected pressure/force information to the host device 20using communication protocols such as Wi-Fi, Bluetooth, etc.

The information (e.g., pressure/force information) transmitted by thestylus 10 is detected by the host device 20 and used to providefunctionality in the display of the host device 20. For example, thehost device 20 may detect that the stylus 10 is in a writing mode withidentifiable pressure/force information. The host device 20 can use thatinformation (in combination with position information detected throughthe digitizer) to display digital ink with a thickness or colordependent on the pressure/force information encoded in the signal. Forexample, a light touch may indicate a relatively finer or lighter lineshould be draw on the display of the touch screen 22. As the userincreases pressure/force on the stylus 10, the weight (e.g. darkness orthickness) of the line may increase accordingly.

Thus, downlink transmission of information is achieved by electrostaticcommunication from the stylus 10 to the digitizer of the host device 20,wherein the digitizer is configured to extract the position of thestylus based on the downlink signal and the stylus 10 may modulate dataon the downlink signal to transmit a pen identity, a force applied onits tip electrode 14, pressure levels, a button indication, etc.

Additionally, uplink transmission of information is achieved via acommunication link from the digitizer of the host device 20 to thestylus 10. The uplink transmission link can be used by the stylus 10 toacquire e.g. digitizer timing and cycle length to be able to ink on thedisplay of the host device 20 and/or receive data from the digitizer,e.g., which frequency shall be used to transmit the downlink signal.

As an example, a touch screen driving signal may be applied to the touchscreen 22. The touch screen driving signal may include an uplink signalfor synchronization with the stylus 10 and a touch sensor driving signalfor sensing a touch input applied to the touch screen 22. When thestylus 10 is brought into contact with the touch screen 22, the stylus10 receives the uplink signal from the touch screen 22, generates adownlink signal (i.e. pen driving signal) in synchronization with thetouch sensor driving signal on the basis of the uplink signal andoutputs the generated downlink signal to the touch screen 22 e.g.through the tip electrode 14. Since the downlink signal is synchronizedwith the touch sensor driving signal, it serves to increase sensitivityof the touch sensor driving signal.

However, in a case a palm or other body portion of a user touches thetouch screen 22 together with the stylus 10, a problem arises in thatthe stylus 10 might fail to properly receive the uplink signal. Here,the palm may be either a palm of a hand gripping the stylus 10 or a handwithout the stylus 10. In this case, the stylus 10 may fail to besynchronized with the touch screen 22 so that no proper operation can beachieved.

FIG. 2 is schematic block diagram indicating capacitances that influencethe strength of an uplink signal during a body touch on a touch screen.

As initially mentioned, a body touch on the touch screen 22 of the hostdevice e.g. by the hand 50 of a user may reduce the strength of theuplink signal received at an input/output unit 12 of a tip receiver viathe tip electrode 14 and a tip capacitance C_(t) of the stylus 10. Theuplink signal is generated at a touch screen driver 25 of the touchscreen 22. Especially, when the host device (e.g. a personal computer)is in a battery mode or connected to the grid via a 2-prong plug withouta connector to earth potential EP1, the ground of the touch screen 22and its digitizer in an in-cell configuration is only coupled to theearth through a system-to-ground capacitance C_(s2g). The hand 50 of auser of the stylus is coupled to the touch screen 22 through a palmcapacitance C_(p) and to earth trough a hand-to-ground capacitanceC_(h2g). Additionally, the stylus ground (i.e. enclosure) is coupled tothe hand 50 of the user via a hand-to-enclosure capacitance C_(h2e)while holding the stylus 10.

In an in-cell configuration, touch sensing elements of the digitizer aredirectly integrated into one or more layers of the display stack of thetouch screen 22 itself. Thereby, the touch sensor substrate can beremoved by combining display cells of the touch screen display and thetouch sensing elements into a single structure, allowing touch screendevices to become thinner and lighter. Former designs with a separatesensor layer are known as out-cell configuration.

Thus, when the user touches the touch screen 22 via his/her hand 50,some of the uplink signal is coupled via the human body of the user tothe pen ground, which reduces the uplink signal that enters the tipelectrode 14 of the stylus 10.

In the following, an example of a calculation of the dependence of theuplink signal at the tip electrode 14 of the stylus 10 from theparasitic capacitances indicated in FIG. 2 is explained in more detail.

The hand potential V_(h) at the hand 50 of the user with reference toground potential V_(ul) of the touch screen 22 can be expressed asfollows:

V _(h) =V _(ul) *C _(p)/(C _(s2g) +C _(p))  (1)

Using the above equation (1), the current I_(t) of the uplink signal atthe tip electrode 14 can then be expressed as follows:

I _(t)=˜(V _(ul) −V _(h))C _(t) s  (2)

I _(t) =˜V _(ul)(1−C _(p)/(C _(s2g) +C _(p)))C _(t) s  (3)

wherein s denotes the complex frequency.

For a typical case where C_(p)=10 pF and C_(s2g)=5 pF, an attenuation ofthe uplink signal by a factor of 0.33 (or −10 dB) is thus obtained.

To mitigate the problem of reduced uplink signal due to a body touch, anuplink channel compensation approach is suggested in embodiments, bywhich the at least one parameter (e.g. channel amplification, spatialdistribution, channel sensitivity etc.) of the uplink channel from thetouch screen driver 25 to the stylus 10 is temporarily modified tocompensate for the signal reduction during a body touch at the touchscreen 22.

FIG. 3 is a schematic flow diagram of an uplink channel compensationprocedure during a body touch.

An initial sensing operation S310 detects parameters of a touch actionat the touch screen 22. This can be achieved by analysing touch row dataaccording to a touch sensor driving signal and the downlink signal ofthe stylus 10 to obtain touch parameters (e.g. capacitance, position,phase, amplitude, single-touch, multi-touch etc.).

More specifically, the touch screen 22 may be implemented as acapacitive touch screen sensing a touch input through a plurality ofcapacitance sensors, wherein capacitance may be classified asself-capacitance and mutual capacitance. The self-capacitance may beformed along a conductor line of a single layer formed in one direction.The mutual capacitance may be formed between two conductor linesperpendicular to each other. The touch sensor may be implemented bymutual capacitance sensors that may include transmission (Tx) electrodelines, reception (Rx) electrode lines intersecting with the Tx electrodelines, and touch sensors formed at intersections of the Tx electrodelines and the Rx electrode lines. The Tx electrode lines are drivingsignal lines supplying electric charges to the touch sensors by applyingthe touch sensor driving signal (and/or the downlink signal of thestylus 10) to the touch sensors. The Rx electrode lines are sensor linesconnected to the touch sensors and supplying electric charges of thetouch sensors to a touch driving device. In a mutual capacitance sensingmethod, electric charges are supplied to the touch sensor by applyingthe touch sensor driving signal (and/or the downlink signal) to the Txelectrodes through the Tx electrode lines, and a change in capacitanceof the touch sensors is sensed through Rx electrodes and the Rxelectrode lines in synchronization with the touch sensor driving signal(and/or the stylus downlink signal), whereby a touch input by aconductive object may be recognized.

Then, a touch analysis operation S320 is performed to analyse at leastone touch parameter. In an example, the touch sensing system of thedigitizer of the touch screen 22 may simultaneously sense two touchinputs, e.g., a body touch input by a body part (e.g. finger or palm) ofa user and a stylus touch input by the stylus 10. The body touch inputmay be sensed on the basis of an analysis result of the touch row dataaccording to the touch sensor driving signal, and the pen touch inputmay be sensed on the basis of an analysis result of touch row dataaccording to the downlink signal of the stylus 10.

In a subsequent discrimination or detection operation S330, theanalyzation result of the touch parameters is used to detect a bodytouch during a concurrent stylus touch by discriminating between astylus touch and a body touch. As an example, the downlink signal of thestylus 10 and the touch sensor driving signal of the digitizer may havethe same phase but the magnitude (e.g. pulse amplitude) of the downlinksignal may be set to be greater than that of the touch sensor drivingsignal, whereby the touch row data of the position that the stylus 10has touched and the touch row data of the position that the body of theuser has touched are differentiated to easily distinguish between thestylus touch input and the body touch input (to thereby detect theconcurrent body touch).

Then, in a subsequent decision operation S340, it is decided whether abody touch has occurred (i.e. has been detected) and a compensation isrequired to adjust the uplink signal. If no adjustment is required, theprocedure jumps back to the sense operation S310 and starts again.Otherwise, if an adjustment is required (e.g. if a body touch has beendetected), the procedure proceeds to a compensation operation S350 whereat least one parameter (e.g. amplification, spatial distribution,sensitivity etc.) of the uplink channel is modified to compensate forthe uplink signal loss or diction due to the detected body touch.

The operations of FIG. 3 may be continuously or intermittently repeated.

In the following, different examples of uplink channel compensationswill be described.

FIG. 4 is a schematic block diagram of an example host device withuplink channel compensation.

Here, the adaptive uplink channel compensation can be achieved bymodifying the spatial distribution of active touch sensor elements(antennas) of the digitizer of the touch screen 22. This can be achievedby locally disabling individual touch sensor elements at the determinedlocation and/or area of the detected body touch to thereby reduce thebody capacitance C_(p) to the uplink signal.

Normally, the uplink signal is transmitted from all sensor elements ofthe touch sensor on the touch screen 22 to improve the capacitance tothe tip electrode 14 of the stylus 10 (e.g. when the stylus 10 hoversabove the touch screen 22).

According to FIG. 4 , the host device 20 comprises a touch screen 22 anda touch screen driver (TSD) 25 which controls a touch sensor (e.g. anarray or matrix of sensor elements or antennas) of the touch screen 22.The touch screen driver 25 applies a touch screen driving signal to thesensor elements of the touch sensors and senses the amount of change inthe charge of the sensor elements to determine a touch input. The touchscreen driving signal includes the uplink signal and a touch sensordriving signal.

Furthermore, the touch screen driver 25 analyses charge variations ofthe touch sensor depending on the presence or absence of a touch input,determines or detects the touch input, and calculates coordinates of thetouch input position.

The touch screen 22 may be configured as an in-cell liquid crystaldisplay (LCD) panel that also includes a touchscreen functionality bypositioning at least one of the touch layers (typically a transmit (TX)layer) under a color filter glass. Furthermore, typically the TX layeris shared with a common electrode (reference layer) of the touch screen22. The touch screen driver 25 may be a capacitive touch screen driverthat is used to measure the capacitance on the array of electrodes(sensor elements), such as an array including multiple transmit (TX)electrodes and multiple receive (RX) electrodes. An integrated circuitof the is typically the integrated circuit (IC) positioned on thesubstrate glass of the LCD which drives the timing and video signals tothe LCD. While the above description is for in-cell LCD, similarstack-ups exist for other display types, such as active-matrix organiclight-emitting diode (AMOLED).

Based on the sensor signals generated by the touch screen driver 25, atouch detector 24 detects touch parameters of touch actions as describedabove in connection with the sensing operation S310 of FIG. 3 .

Additionally, the downlink signal received by the touch detector 24 fromthe touch screen driver 25 is forwarded to an ink control (INK-CTRL)application or unit (e.g. a drawing application or unit) 21, where it isutilized to generate digital ink at a determined location of the stylus10 with a weight (e.g., thickness or darkness) or other ink parametercorresponding to a reported force, pressure or inking level included inthe downlink signal.

The touch parameters determined by the touch detector 24 are provided toa body touch detector (BTD) 28 of the digitizer, which is configured toidentify a location of a body portion (e.g. hand or finger) on the touchscreen as described above in connection with the touch analysis anddiscrimination or detection operations S320 and S330 of FIG. 2 . Basedon the identified location of a detected body touch, the body touchdetector 28 controls the touch screen driver 25 so that selected sensorelements of the touch sensor at or around the location the detected bodytouch are disabled to thereby reduce the amount of uplink signal lossvia the partial uplink channel path through the capacitance C_(p).

As an example, the body touch detector 28 of the digitizer may initiatea control operation by the touch screen driver 25 to disable theselected sensor elements by connecting them to ground potential oranother reference potential to thereby reduce an excited uplink signalon the body portion of the user.

In another embodiment, the adaptive uplink channel compensation can beachieved by modifying the amplification of the uplink signal at thetouch screen driver 25 of the touch screen 22. This can be achieved bycontrolling an amplification factor of an amplifier of the touch drivercircuit 25. More specifically, based on a detected body touch, the bodytouch detector 28 controls the touch screen driver 25 of the digitizerso that the level of the uplink signal is increased to compensate anysignal reduction caused by the body touch and ensure good inkingperformance. Normally, the digitizer may transmit the uplink signal witha low or moderate power or voltage. When, a body touch is indicted bythe body touch detector 28, the touch screen driver 25 can be controlledby the body touch detector 28 to boost the voltage or power of theuplink signal momentarily or temporarily to improve the inkingperformance at the ink control unit or application 21.

It is noted that the spatial modification (e.g. selective disabling) ofthe selected sensor elements of the touch sensor may be combined withthe modification of the amplification factor of the touch screen driver25 to obtain a more effective compensation of the uplink signalreduction during a body touch.

The touch detector 24, the touch screen driver 25, the body touchdetector 28, the ink control unit or application 21 and other systemcomponents of the host device 20 may be implemented in an applicationspecific integrated circuit (ASIC), a system on chip (SOC), a fieldprogrammable gate array (FPGA), a micro-processing unit, etc.

FIG. 5 is a schematic block diagram of an example host device 20 withuplink channel compensation at an active stylus 10. In this example, theuplink channel compensation is achieved by modifying the sensitivity ofa reception unit (Rx) 13 of the stylus 10.

The tip electrode 14 of the stylus 10 may be formed of a conductivematerial such as a metal, or the like, and protrudes outwardly from oneside of the housing to serve as an input/output electrode. Since the tipelectrode 14 serves as an input/output electrode, a structure of thestylus 10 is advantageously simplified. When the tip electrode 14touches the touch screen 22 of the host device 20, the tip electrode 14is coupled to the touch screen 22 in the contact point. The tipelectrode 14 receives a touch screen driving signal (uplink signal) fromthe touch screen 22 at the contact point and outputs a pen drivingsignal (downlink signal) produced within the stylus 10 to the contactpoint of the touch screen 22. When the tip electrode 14 touches thetouch screen 22 of the host device 20, the input/output unit 12 of thestylus 10 electrically connects the tip electrode 14 and a receptionunit 13 during a reception period, and electrically connects the tipelectrode 14 and a transmission unit (Tx) 15 during a transmissionperiod to thereby temporally separate a reception timing of the uplinksignal (touch screen driving signal) and a transmission timing of thedownlink signal (pen driving signal).

The reception unit 13 comprises at least one amplifier and at least onecomparator and digitally processes the uplink signal input through theinput/output unit 12 during the reception period.

The stylus 10 may further comprise one or more processing units (e.g.controller (CTRL)) 18 e.g. with a memory for onboard storage of userfiles, user specifications, etc. The memory may be a tangibleprocessor-readable storage and may store processor readable instructionsfor communication and digital inking through the host device 20. Thestylus 10 may comprise a display (not shown) that may display to theuser any of the following: the power status of the battery, the currentwireless signal strength, or other information relating to the hostdevice 20 configured to receive user input from the stylus 10.

The processing unit 18 may analyse a pattern (i.e., pulse duty, numberof pulses, and the like) of the uplink signal to check its validity.When a normal uplink signal is detected, the processing unit 18determines that the uplink signal is valid and generates a pen drivingsignal (downlink signal) synchronized with a touch sensor driving signalincluded in the uplink signal. The processing unit 18 may refer tosignal generation conditions (e.g. period, duty, number, and the like)of a default parameter set installed to generate the downlink signalsynchronized with the touch sensor driving signal. The processing unit18 then outputs the downlink signal to the tip electrode 14 through theinput/output unit 12 during a transmission period of a touch period.

The stylus 10 may further comprise a wireless communication unit (WCU)17. The wireless communication unit 170 may be configured to communicatewith the host device 20 via Bluetooth, Wi-Fi, near-field communication(NFC), etc. The wireless communication unit 17 may include a receiver toreceive communication commands, pairing requests, etc. from a wirelesscommunication unit (WCU) 27 at the host device 20. The stylus 10 mayfurther comprise a power supply (not shown), which may comprise abattery for powering the various components of the stylus 10. Thebattery may be rechargeable, replaceable, disposable, etc.

In some examples, the stylus 10 may additionally or alternatively bewired to the host device 20, for example, by a Universal Serial Bus(USB) connection and may communicate with the host device via such aconnection.

Furthermore, the processing unit 18 may be configured to control thesensitivity of the reception unit 13 based on a feedback signal (FS)received from the host device 20 via the wireless communication unit 17.The sensitivity control may be achieved by temporarily applying a biasvoltage to at least one amplifier of the reception unit 13 to controlthe receiver gain. Such gain control may be necessary to adjust thesensitivity of the reception unit 13 for a better reception of theuplink signal in case of a decreased uplink signal level due to a bodytouch.

Thus, in the present example, the adaptive uplink channel compensationcan be achieved by modifying the sensitivity of the reception unit 13 atthe stylus 10. More specifically, in response to a detected body touch,the body touch detector 28 forwards the feedback signal indicating abody touch event to a transmitter of the wireless communication unit 27of the host device 20, which transmits the feedback signal to a receiverof the wireless communication unit 17 of the stylus 10. The wirelesscommunication unit 17 of the stylus 10 forwards the received feedbacksignal to the processing unit 18 which generates a sensitivity controloutput to control the sensitivity of the reception unit 13 so that thelevel of the uplink signal is momentarily or temporarily increased tocompensate for any signal reduction of the uplink signal caused by thebody touch.

As a further example, the feedback signal may indicate different levelsof sensitivity control output to provide an adaptive sensitivity controlat the receiver 12 in dependence on the area and/or strength of the bodytouch and a resulting estimated reduction of the level of the uplinksignal.

The stylus 10 may further comprise a force or pressure sensor (notshown) with an optional force or pressure response circuit (not shown),which together with the processing unit(s) 18 may collectively bereferred to as the inking system. The inking system detects force orpressure applied to the tip electrode 14, optionally increases force orpressure sensitivity, converts the detected force or pressure to anoutput value (e.g. reported (inking) level) and communicates the outputvalue to the host device 20.

As an example, the output value may be an encoded digitizer signal (i.e.the downlink signal) and transmitted to the digitizer of the host device20. At the host device 20, the received output value is detected andforwarded to the ink control application or unit (e.g. a drawingapplication or unit) 21, where it is utilized to generate digital ink ata determined location of the stylus 10 with a weight (e.g., thickness ordarkness) or other ink parameter corresponding to the adapted andreported force, pressure or inking level.

The input/output unit 12, the reception unit 13, the transmission unit15, the processing unit(s) 18 and other system components of the stylus10 may be implemented in an application specific integrated circuit(ASIC), system on chip (SOC), a field programmable gate array (FPGA), amicro-processing unit, etc.

The stylus 10 may include one or more buttons (not shown) for changingoperational modes of the stylus. For example, when button is depressed asignal communicated to the host device may inform the host device thatthe stylus 10 is in an erasure mode. Furthermore, such operational modesmay indicate a color of the digital ink, writing patterns (e.g., dottedlines), writing utensil (e.g., brush, pen, marker, pencil). The detectedforce or pressure may be indicated with different operational modes. Forexample, when in an erasure mode, the detected force or pressure mayindicate an erasure thickness. The buttons may also be used to initiatea device pairing with the host device 20.

In examples, the stylus body may be formed of a material suitable forenclosing the components described herein. The stylus body may be formedfrom, for example without limitation, plastic, rubber, metal, carbonfiber, etc. and/or any combinations thereof.

It is noted that at least one of the above described spatialmodification of the sensor elements of the touch sensor and the abovedescribed modification of the amplification factor of the driver at thehost device 20 may be combined with the above described sensitivitycontrol of the reception unit 13 at the stylus 10 to obtain a moreeffective compensation of the uplink signal reduction during a bodytouch.

To summarize, the effect of a contact by a hand or other body part of auser with a touch screen (while holding an input device (e.g. stylus oreraser or the like)) on the strength of a capacitively coupled uplinksignal provided to the input device by a host device is mitigated bydetecting and/or discriminating the body touch and modifying at leastone uplink channel parameter to compensate the effect on the uplinksignal. The channel compensation can be achieved by detecting a positionof the body touch and using this detected position to selectivelydisable sensing elements of a touch sensor (modification of the spatialdistribution of the uplink channel), so that the uplink signal is notsupplied to touch screen sensing elements that are located in the areaof the detected body touch. Alternatively or additionally, the channelcompensation can be achieved by at least one of increasing anamplification of a touch screen driver to increase the level of thetransmitted uplink signal (modification of the amplification of theuplink channel) or increasing the sensitivity of a receiver at the inputdevice to increase the level of the received uplink signal.

It will be appreciated that the above embodiments have been described byway of example only. The invention can be applied to any type of touchscreen system with any type of input device that may involve a bodytouch of a user. The touch screen 22 may be implemented on the basis ofa liquid crystal display (LCD), a field emission display (FED), a plasmadisplay panel (PDP), an organic light emitting display device, anelectrophoresis display, and the like.

More generally, according to a first aspect disclosed herein, there isprovided an apparatus for controlling an inking process by an inputdevice on a touch screen, the apparatus comprising:

a body touch detector for detecting a body touch by a body portion of auser on the touch screen during a concurrent touch by the input device;and

a modulator for temporarily changing at least one transmission parameterof an uplink channel from a touch screen driver of the touch screen to areceiver of the input device in response to a detected body touch.

In embodiments, the modulator may be configured to modify the uplinkchannel by temporarily increasing an amplification factor of the touchscreen driver in response to the detected body touch.

In embodiments, the modulator may be configured to determine a locationof the body touch on the touch screen and to modify a spatialdistribution of the uplink channel by disabling selected sensor elementsof a touch sensor of the touch screen at the determined location of thebody touch in response to the detected body touch.

In embodiments, the modulator may be adapted to disable the selectedsensor elements by connecting them to a reference potential.

In embodiments, the modulator may be configured to modify the uplinkchannel by temporarily increasing a sensitivity of the receiver at theinput device in response to the detected body touch.

In embodiments, the modulator may be adapted to increase the sensitivityof the receiver at the input device by signalling a body touch feedbacksignal from a host device of the touch screen to the input device.

In embodiments, the modulator may be configured to increase thesensitivity of the receiver by initiating a gain control of an amplifierof the receiver.

In embodiments, the apparatus of the first aspect may comprise awireless communication unit for signalling the body touch feedbacksignal to the input device.

According to a second aspect disclosed herein, there is provided a hostdevice or digitizer comprising an apparatus of the first aspect, a touchscreen and a touch screen driver.

According to a third aspect disclosed herein, there is provided anapparatus for controlling an inking process by an input device on atouch screen, the apparatus comprising:

a communication unit for receiving a body touch feedback signal from ahost device of the touch screen; and

a sensitivity controller for controlling the sensitivity of a receiverfor receiving an uplink signal from a touch screen driver of the touchscreen, in response to a receipt of the body touch feedback signal.

According to a fourth aspect disclosed herein, there is provided aninput device comprising an apparatus of the third aspect and a receiverfor receiving an uplink signal from a touch screen driver of a touchscreen.

In embodiments, the input device may comprise a stylus or an eraser.

According to another aspect disclosed herein, there is provided a methodof controlling an inking process by an input device on a touch screen,the apparatus comprising:

detecting a body touch by a body portion of a user on the touch screenduring a concurrent touch by the input device; and

temporarily changing at least one transmission parameter of an uplinkchannel from a touch screen driver of the touch screen to a receiver ofthe input device in response to a detected body touch.

According to another aspect disclosed herein, there is provided a methodof controlling an inking process by an input device on a touch screen,the apparatus comprising:

receiving a body touch feedback signal from a host device of the touchscreen; and

controlling a sensitivity of a receiver for receiving an uplink signalfrom a touch screen driver of the touch screen, in response to a receiptof the body touch feedback signal

According to another aspect disclosed herein, there is provided acomputer program embodied on computer-readable storage and comprisingcode configured so as when run on one or more processors to perform themethod of any embodiment disclosed herein.

Examples and embodiments described herein may be implemented as logicalsteps in one or more computer systems. The logical operations may beimplemented (1) as a sequence of processor-implemented steps executingin one or more computer systems and (2) as interconnected machine orcircuit modules within one or more computer systems. The implementationis a matter of choice, dependent on the performance requirements of thecomputer system used for implementation. Accordingly, logical operationsmaking up examples or embodiments described herein may be referred tovariously as operations, steps, objects, or modules. Furthermore, itshould be understood that logical operations may be performed in anyorder, adding and omitting as desired, unless explicitly claimedotherwise or a specific order is inherently necessitated by the claimlanguage.

Other variants and applications of the disclosed techniques may becomeapparent to a person skilled in the art once given the presentdisclosure. The scope of the present disclosure is not limited by theabove-described embodiments but only by the accompanying claims.

1. An apparatus for controlling an inking process by an input device ona touch screen, the apparatus comprising: a body touch detector fordetecting a body touch by a body portion of a user on the touch screenduring a concurrent touch by the input device; and a modulator fortemporarily changing at least one transmission parameter of an uplinkchannel from a touch screen driver of the touch screen to a receiver ofthe input device in response to a detected body touch, wherein themodulator is configured to modify the uplink channel by temporarilyincreasing an amplification factor of the touch screen driver inresponse to the detected body touch or by signalling a body touchfeedback signal, used for temporarily increasing a sensitivity of thereceiver, to the input device in response to the detected body touch. 2.The apparatus of claim 1, wherein the apparatus comprises a wirelesscommunication unit for signalling the body touch feedback signal to theinput device.
 3. An apparatus for controlling an inking process by aninput device on a touch screen, the apparatus comprising: acommunication unit for communicating with a host device of the touchscreen; and a sensitivity controller for controlling the sensitivity ofa receiver for receiving an uplink signal from a touch screen driver ofthe touch screen, wherein the communication unit is configured toreceive a body touch feedback signal from the host device of the touchscreen; and wherein the sensitivity controller is configured to controlthe sensitivity of the receiver in response to a receipt of the bodytouch feedback signal.
 4. The apparatus of claim 3, wherein thesensitivity controller is configured to increase the sensitivity of thereceiver by initiating a gain control of an amplifier of the receiver.5. An input device comprising an apparatus of claim 3 and a receiver forreceiving an uplink signal from a touch screen driver of a touch screen.6. The input device of claim 5, wherein the input device comprises astylus or an eraser.
 7. A host device comprising an apparatus of claim1, a touch screen and a touch screen driver.
 8. A method of controllingan inking process by an input device on a touch screen, the method beingperformed at a host device and comprising: detecting a body touch by abody portion of a user on the touch screen during a concurrent touch bythe input device; temporarily changing at least one transmissionparameter of an uplink channel from a touch screen driver of the touchscreen to a receiver of the input device in response to a detected bodytouch; and performing the modification of the uplink channel bytemporarily increasing an amplification factor of the touch screendriver in response to the detected body touch or by signalling a bodytouch feedback signal, used for temporarily increasing a sensitivity ofthe receiver, to the input device in response to the detected bodytouch.
 9. (canceled)
 10. A computer program embodied on acomputer-readable storage and comprising code configured to cause theapparatus of claim 1 to perform a method of controlling an inkingprocess by an input device on a touch screen, the method being performedat a host device and comprising: detecting a body touch by a bodyportion of a user on the touch screen during a concurrent touch by theinput device; temporarily changing at least one transmission parameterof an uplink channel from a touch screen driver of the touch screen to areceiver of the input device in response to a detected body touch; andperforming the modification of the uplink channel by temporarilyincreasing an amplification factor of the touch screen driver inresponse to the detected body touch or by signalling a body touchfeedback signal, used for temporarily increasing a sensitivity of thereceiver, to the input device in response to the detected body touch.